A/N 1: So this idea came to me while I was re-watching Fireside Girl Jamboree. At the beginning of the episode, Candace is sitting at her computer trying to get tickets to the Paisley Sideburn Brothers concert. She's sleeping at the computer, but wakes up a loud noise and discovers that Phineas and Ferb were up most of the night cleaning up their project from the previous day. So this idea was sort of like "did Phineas and Ferb stay up all night cleaning and having long talks? Did they start to fall asleep but managed to keep each other awake enough to clean? Did they goof off? Use your imagination and go nuts!
A/N 2: This was originally for a Phineas and Ferb as brothers story, but if you want to change that into a Phineas-and-Ferb-as-a-couple-story, go for it.
It's a night of brotherly bonding as Phineas and Ferb stay up, cleaning up a project that inexplicably failed to disappear.
Would take place the night before/morning of Fireside Girl Jamboree